A.c.energized magnetic particle flaw detector with means to raise and lower electromagnets from path of workpiece

ABSTRACT

AN ARRANGEMENT FOR CONTINUOUS MAGNETIC FLAW DETECTION FOR STEEL MATERIALS COMPRISING SPRAYING MAGNETIC PARTICLES SUSPENDED IN A LIQUID OVER A STEEL MATERIAL UNDER INSPECTION SUCH AS A LONG SQUARE BILLET WHILE SAID MATERIAL IS MOVED JUST BEFORE BEING MAGNETIZED, AND MAGNETIZING THE PARTICLESPRAYED MATERIAL ACCORDING TO BY AN ALTERNATING MAGNETIC FIELD OF A MAGNETIZING DEVICE INCLUDING AN ALTERNATING CURRENT ELECTROMAGNET WITHOUT BRINGING THE INSPECTED MATERIAL INTO CONTACT WITH THE MAGNETIZING SYSTEM.   D R A W I N G

United States Patent 1 Suzuki et al.

[ Jan. 8, 1974 Lorenzi.........t......................

324/38 324/38 10/l970 Forsten.........................l.......

FOREIGN PATENTS OR APPLICATIONS A.C. ENERGIZED MAGNETIC PARTICLE 3,480,855 11/1969 FLAW DETECTOR WITH MEANS o RAISE 3,243,875 4/1966 Il10................. AND LOWER ELECTROMAGNETS FROM 3534258 PATH 0F WORKPIECE Takeriobu Suzuki; Buemon [75] Inventors:

Nagashima, both of Tokyo; Masayoshi Inoue; Yoji Ito, both of Yokosuka City, all of Japan [73] Assignee: Tokushu Toryo Co. Ltd., Tokyo,

[57] ABSTRACT An arrangement for continuous magnetic flaw detecaaen .7

[22] Filed: Sept. 1, 1970 [21] Appl. No.: 68,621

tion for steel materials comprising spraying magnetic particles suspended in a liquid over a steel material billet while said material is moved just before being magnetized, and

-sprayed material according to by an alternating magnetic field of a magnetizing device including an alternating current electromagnet without bringing the inspected material into contact 2 Claims, 13 Drawing Figures u S m m T mm mmm N I "m" m ml m m 0 m mnm .mM ma J- f C .mh nu Sit 7 u S 38 6 cc m m mmmm m mT m mu .WSDD "uh eD R nu -m E23 e T S mm .1 mi W C m WM A e 0 i 12 UHF 2 2H8 6 mm 555 5 9s [[rlL I 23 PATENIEU 81974 3. 784. 904

SHEET 1 0F 3 I NVENTOR.

A.C. ENERGHZED MAGNETIC PARTICLE FLAW DETECTOR WITH MEANS TO RAISE AND LOWER ELECTROMAGNETS FROM PA 2 F WORKPIECE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates in general to a method of continuous magnetic flaw detection for steel material and an apparatus therefor, and more particularly to a method and apparatus for the continuous magnetic flaw detection and removal for steel material such as long square billets, wherein the inspected material, for example, a long square billet can be continuously inspected for surface defects such as surface flaws, and wherein the surface defects thus detected can be continuously removed by grinding following said inspection.

2. Description of the Prior Art As a conventional method for detection of surface flaws and similar defects of metal material such as steel material, the magnetic particle inspection method has been widely employed by virtue of its high reliability, detection sensitivity etc. This method is to detect surface defects of a steel material by attaching magnetic particles onto the surface defects (hereinafter simply referred to as flaws) by making use of magnetism, and is broadly classified into the following three methods: (a) The method of detecting flaws by the lines of magnetic force produced by directly passing a great current through the material under inspection. In this process, the lines of magnetic force are generated in the circumferential direction of thematerial so as to allow detection of flaws extending at right angles to said lines, that is, flaws in parallel with the longitudinal direction of the material. (b) The method of flaw detection by the lines of magnetic force generated by passing current through a magnetizing coil surrounding the material subjected to inspection. In this method, the lines of magnetic force take place in the longitudinal direction of the subject, thus making it possible to detect flaws directed at right angles to said lines, namely, at right angles to the longitudinal direction of the material. (c) The method of detecting the flaws of the material by the lines of magnetic force produced between the poles of an electromagnet. Just like the preceding method (a), this method is capable of detecting flaws perpendicular to the lines of magnetic force.

In the case where it is intended to inspect a long steel material such as a square billet, only flaws in the longitudinal direction come into question as to what should be detected. In view of this fact, the second method (b) of the above three is not applicable in this case since it is not a method for detection of flaws in the longitudinal direction. Thus, the methods (a) or (c) are applicable. The method (a) has so far found a relatively wide variety of applications. However this method requires a special electric system for supplying a large current, and also makes it necessary to flow current through the material inspected with both ends firmly fastened, thus being beset with a low working efficiency and liable to give rise to faulty contact. With these drawbacks, this method is not suitable for continuous detection of flaws in long square billets and the like.

On the other hand, the method (c), which employs an electromagnet, requires no such great current as the method (a) does. For this reason, portable apparatus of the interpole space type and the like which adopt this method have hitherto been widely used. Nevertheless, this method (0) is applicable only to small-sized materials since the size of the material surface to be inspected is limited by the space between the poles. Thus, this method is not suited to flaw detection in long square billets. In an attempt to improve this point, the Japanese Utility Model Publication No. 7697/ 1958, for example, discloses an inspection apparatus in which, with the spacing between the electromagnet poles widened, the material under inspection is sprayed with magnetic particles while the material is moved between the poles. In this apparatus, however, the pole portions at the ends are made small in view of the efficiency of the magnetic circuit. Moreover, the long materials regarded as objects of the inspection are round bars, pipes, and so on. Hence, the prior art apparatus as described above is not suitable for continuous flaw'detection for long steel material such as long square billets.

Furthermore, because of the difficulty in the continuous flaw detection for long materials, it is difficult to use the conventional methods (a) and (c) hereinbefore described, and in working out a continuous arrangement for direct connection with a flaw removing system, i.e., to construct a continuous flaw detecting and removing apparatus. Thus, heretofore, there has thus been no alternative but to install the flaw detecting system and the flaw removing system separately. Therefore it has been necessary to do such troublesome work as carrying a long square billet to the flaw removing apparatus after the completion of flaw detection and subjecting the detected flaws to grinding by the removing system. Besides, some of the flaws are hard to remove by a single grinding operation, so that flaw detection and flaw removal by grinding have always been a repetitive troublesome operations.

OBJECTS OF THE INVENTION An object of this invention is to improve the aforesaid prior method which employs an electromagnet, to solve the conventional problems, thereby providing a method and apparatus for continuous magnetic particle inspection of steel material in which continuous magnetic flaw detection can be performed, with the additional possibility of continuous flaw removal following said flaw detection.

Another object of this invention is to provide a method and apparatus for continuous magnetic flaw detection for steel material wherein it is possible to detect the flaws, particularly in a long steel material such as a square billet in continuous and reciprocating motion at a relatively high speed, with the additional possibility of flaw removal by grinding corresponding to the continuous and reciprocating flaw detecting operation.

Still another object of the invention is to provide an apparatus for automatic and continuous magnetic flaw detection for steel material, particularly, long steel material such as square billets which can automatically carry out flaw detection removal with high efficiency, scarcely requiring operator attendance.

SUMMARY OF THE INVENTION In order to attain these objects, the present invention contemplates the means of spraying magnetic particles suspended in a liquid over a steel material under inspection such as a long square billet while said material is moved just before being magnetized, and the means of magnetizing the particle-sprayed material according to its movement by the alternating magnetic field of a magnetizing system including an alternating current electomagnet without bringing the material into contact with the magnetizing system. Furthermore it is possible according to the present invention to provide an automatic and continuous flaw detecting and removing apparatus by using the continuous flaw detecting systems of this invention in connection with the front and rear of a flaw detecting system, and also by using these systems in combination with electrical and optical means capable of monitoring and marking. These features of the present invention will be described in more detail hereunder. The invention provides a method of continuous magnetic flaw detection which comprises spraying magnetic particles suspended in a liquid continuously from one direction over a surface of a long square billet traveling on a roller table, continuously moving the square billet sprayed with the suspended magnetic particles between the poles of an a.c. electromagnet and magnetizing the billet by the alternating magnetic field for flaw detection, and thereafter, if necessary, turning over the flawdetected square billet and returning the billet onto said roller table to subject another billet surface remaining uninspected to magnetic particle spraying and magnetic flaw detection in the same way as described above, thereby continuously detecting flaws all over the surfaces of the square billet. The invention also provides for an apparatus for continuous magnetic flaw detection and flaw removal constructed by combining said apparatus for continuous magnetic flaw detection of this invention with a flaw removing apparatus having a high-speed grinder in such a manner that the continuous flaw detecting apparatus is installed in connection with the front and rear of said flaw removing apparatus, or provides an apparatus for automatic and continuous magnetic flaw detection and flaw removal characterized by combining said apparatus for continuous flaw detection and removal with such electrical and optical devices as industrial television cameras, tape recorders, a marking device, and an electrical system for connecting and operating these devices.

BRIEF DESCRIPTION OF THE DRAWINGS The objects and features of this invention will be more fully understood from the following description taken in conjunction with the accompanying drawings, in which:

FIG. I is a perspective view showing an apparatus embodying the present invention:

FIG. 2 is an enlarged perspective view of a composing system of the arrangement shown in FIG. 1;

FIG. 3A, and FIG. 3B are perspective views showing the operation of a part of the arrangement of FIG. ll;

FIG. 4 is an enlarged perspective view of part of the arrangement of FIG. ii;

FIG. 5 is a schematic front view of another system embodying the invention;

FIG. 6A and FIG. 6B are sectional views each showing a magnetizing system provided in the arrangement shown in FIG. 5;

FIGS. 7A, 7B and 7C are illustrations each showing the relation between the surface flaws of a magnetized material and the lines of magnetic force:

FIGS. 8A and SB are illustrations each showing the relation between the sectional shape of a piece of steel material and the magnetic flux passing through the material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the attached drawings showing preferred embodiments of the present invention, and more particularly to FIG. I, which shows a continuous magnetic flaw detecting and removing method and apparatus embodying the invention, a long square billet l to be inspected is moved on a material carrying floor 2 on the supply side in the direction of the arrow until it is dropped on a roller table A equipped with a multipilicity of rollers 3. The square billet 1 is then advanced in the direction of the arrow by means of the rollers 3, which are driven by the gearing housed in a driving gear box 4. The square billet 1 thus advanced has its moving position corrected by a guiding system B driven by hydrauric pressure, or the like and passes under the succeeding magnetic particle sprayer C. The guiding system B is composed of a fixed arm 5 on one side and a pushable arm 6 on the opposite side, the latter being actuated by hydraulic pressure. By the operation of the pushable arm 6 the position of the traveling square billet l is corrected so that the billet 1 is accurately shifted through the sprayer C into the space between the magnetic poles of the subsequent magnetizing system D.

As seen in the enlarged perspective view of FIG. 2, the magnetic particle sprayer C comprises a tank 7 receiving magnetic particles suspended in a liquid, a multiplicity of spray nozzles 8, and suspension supply and discharge pipes 9 and 10 respectively. As described above, the present invention employs magnetic particles suspended in a liquid (hereinafter simply referred to as suspended magnetic particles), and a colorant or a fluorescent matter is attached to the suspended magnetic particles, as required. The suspended magnetic particles are sprayed all over the surface of the square billet ll passing just under the magnetic particle suspension sprayer C toward the spacing between the poles of the subsequent magnetizing system D. While the suspended magnetic particles sprayed are partly deposited all over the square billet 1, the remaining magnetic particle suspension flows down into a suspension recovery tank 11 provided below, and the suspension thus recovered is returned up to the suspension supply tank 7 for circulation. The reference numeral 20 stands for a spare suspension tank.

When the square billet l to which suspended magnetic particles are attached as described hereinbefore gets into the magnetizing system D equipped with the a.c. electromagnet, the deposited magnetic particles are immediately attracted together to the flaws by the alternating magnetic field and thus a magnetic particle pattern is formed. The present invention does not employ any such direct current power source as used with the conventional electromagnet, but employs an alternating current power source specifically. By applying this a.c. power supply to the magnetizing system furnished with the electromagnet, not only the generation of alternating magnetic force lines but also current induction in the material under inspection is effected. It is thus intended to utilize also the alternating magnetic force lines caused by the induced current, which cooperate with the above stated alternating magnetic force lines. This co-operative effect results in the formation of so clear a magnetic particle pattern on the surface of the material that the flaws can be removed with much ease. It should be noted that the use of a direct current does not allow any effective flow of magnetic particles to occur on the surface of the material. In the present invention, the application of such alternating magnetic field and the spraying of suspended magnetic particles just before the aforesaid magnetization make it possible to carry out continuous detection of the flaws of the long square billet 1.

The magnetic poles are so spaced that, when the square billet i is advanced between the poles, there exists an adequate gap g to keep the billet I out of contact with the poles. The size of the gap g is preferably less than one-fourth of the length of a side of the square billet I.

The magnetizing system D is composed of the electromagnet 12, which is a U-shaped one, an electromagnet base 13, and a lifting system E provided under the electromagnet base T3 to move the base vertically. The lifting system B comprises a cylinder-piston assembly 14 located at the center, the piston being actuated by hydraulic pressure, compressed air, or the like, and four vertically extendible guide poles 15 positioned at the four corners. The electromagnet 12 on the base 13 is moved up and down arbitrarily by operating the cylinder-piston assembly 14. By thus vertically moving the electromagnet 112, it is possible to prevent the electromagnet 12 from being damaged when the square billet l with one of its surfaces inspected is turned over for another surface to be inspected or when the square billet 1 having undergone flaw detection or removal is moved back. Otherwise, the long square billet 1, while moving, might come into contact with the electromagnet 12 and damage the coil since said billet 1 generally has distortion, curvature or the like in the longitudinal direction. In addition, the provision of the lifting system B for the electromagnet 12 makes the flaw detecting apparatus relatively shorter in length and more efficient, and also makes it possible to provide such an efficient system as is constructed by installing a flaw removing system in connection with the flaw detecting apparatus especially for long square billets and similar long materials.

The magnetic particle pattern continuously formed over the flaws of the long square billet l by the magnetizing system D is made easier to observe by an irradiation system such as a black light projector F following the magnetizing system D and is removed by the flaw removing grinder 16 of the flaw removing system G provided in connection with the black light projector F. The flaw removal by grinding is performed by the operator 18, at the center who watches and removes the flaws, operating a control board 19. However, the removing operation can be automated by employing the system shown in FIG. 5, as will be described later.

The square billet 1 having the surface flaws removed is shifted onto a roller table H on the discharge side, shown at left, and is turned over on the table II so that another surface not yet inspected faces upward. The billet 1 thus overturned is moved in the reverse direction through another magnetic particle suspension sprayer C connected to the roller table H and having the same construction as the aforesaid sprayer C, and through another magnetizing system D provided in connection with the sprayer C. The flaws detected on the other surface is removed by the flaw removing system G. After complete removal of flaws from said other surface, the square billet I is returned to the roller table A on the supply side and turned over again. Then another as yet uninspected surface of the square billet l is subjected to flaw detection and removal in the same manner as described already. In this way, the square billet I is reciprocated through both magnetizing system on the supply and discharge sides and the intermediate flaw removing system until the flaws all over the four circumferential surfaces are removed. Besides, in case the flaws on a surface of the square billet 1 is not completely removed by a single removing operation, the surface is subjected to repetitive flaw detection and removal by the grinder 16 of the flaw removing system G until the surface flaws are all eliminated. Thus, the continuous arrangement enables all the reciprocating or repetitive flaw detecting and removing operations to be continuously performed, so that the long square billet 1 can undergo a pronouncedly efficient flaw removing operation.

In such operations as the reciprocation of the long square billet 1, it is necessary, as described hereinbe fore, to lift and lower the electromagnet 12 of the magnetizing system D. Reference in now made to FIG. 3A and 3B. The electromagnet 12 is lowered as shown in FIG. 3A and normally kept in this position. When magnetization is required, the electromagnet I2 is raised as shown in FIG. 3B. These lifting and lowering operations are all controlled on the control board 19 of the flaw removing system G. However, they can be automated by providing an adequate electric system 17 or the like in the vicinity of the magnetizing system D, for example.

In order to eliminate surface flaws from the long square billet 1 by means of the flaw removing system G, it is necessary to move the billet 1 while maintaining it in a correct position on the roller table. For this pur pose, a pinch roller system as shown in FIG. 4 by way of example is arranged on each of the front and rear sides of the flaw removing system G. This roller system comprises a rotatable and movable vertical roller 21 and two fixed vertical rollers 22. The square billet I can be advanced while kept in a predetermined position by the movable roller 21.

The relation between lines of magnetic force and surface flaws is shown in FIGS. 7A, 7B, 7C. With respect to the surface flaw 31 of the material 30 under inspection, the lines of magnetic force are at right angles in FIG. 7A, in parallel in FIG. 7B, and normal in FIG. 7C. In the cases of FIGS. 7 B and 7C, no sufficient leakage flux is produced from the surface flaw 31, which therefore can not be detected. In the case of FIG. 7A, it is not possible to detect flaws in the other surfaces of the material 30 than the opposed surfaces. More particularly, as shown in FIG. 8A the lines of magnetic force generated by the electromagnet 32 are directed as indicated by the arrows in respect to the material 30, which is shown as a square billet, so that the effectively inspectable surfaces of the square billet are the two opposite surfaces, that is, a half of all the surfaces. Where the material 30 is a round bar, the magnetic force lines pass as shown in FIG. 8B, and hence the effectively inspectable surface area of the round bar is about onefourth of the total surface area. Thus, when using a magnetizing system provided with an electromagnet in such a way as in the present invention, it is necessary to pass a square billet at least twice through the magnetizing system and a round bar at least four times.

As described hereinabove, after a surface of the long square billet 1 has its flaws detected by the flaw detecting system comprising the magnetic particles suspension sprayer C and the magnetizing system D and removed by the flaw removing system G, the square billet 1 is turned over and another surface of the billet 1 is inspected by the other similar flaw detecting system comprising the other magnetic particle suspension sprayer C and magnetizing system D and deprived of the flaws by the flaw removing system G. In this way, the reciprocation and overturning of the square billet l is carried on so that the remaining surfaces undergo flaw detection and removal one after another. Thus, the present invention makes it possible to subject all the surfaces of the long square billet l to continuous flaw detection and removal.

The apparatus of the invention which is shown in FIG. 1 may be modified in the combination of the flaw detecting and removing systems. That is, it is possible to detect the flaws in all the surfaces by reciprocating the square billet 1 through a single fiaw detecting system and to mark all the flaws by using a monitor and a marking device in combination with the flaw detecting system, the marked flaws being removed by the grinding operation of flaw removing system provided in connection with said flaw detecting system.

An alternative embodiment of the invention is illustrated in FIG. 5. In the arrangement shown, two magnetizing system J and J are connected in series so as to effect continuous detection of the flaws in all the four surfaces of the square billet 1. The flaws thus detected are continuously marked on the surfaces of the square billet 1 by electric and optical system comprising two monitors K and K, a marking system L, etc. as will be described hereinafter, and the billet 1 with the flaws marked is passed to a flaw removing system following the marking system L.

In the above described two magnetizing systems J and J, the positions of electromagnets 33 and 33 are shifted 90 degrees from each other as shown in FIGS. 6A and 68 so that the XX and YY surfaces, that is, all of the four surfaces can be inspected. On the other hand, the feed rollers 34 for the square billet 1 are V-shaped. Thus the square billet 1 can always be moved between the poles of the electromagnets 33 and 33 which are 90 discrepant in position.

In FIG. 5, the letters C and C denote magnetic particle suspension sprayers. The monitors K and K pick up the magnetic particle patterns formed over surface flaws to convert the patterns into electric signals. The letters M and M refer to memory-delay units which transmit the electric signals from the monitors K and K to the marking device L with time lags. The marking device L is provided in succession to the magnetizing system J and J and operated by the electric signals transmitted from the monitors K and K through the memory-delay units M and M. The square billet 1 is advanced in the direction of the arrow. The monitors K and K comprise, for example, four industrial television cameras, one for each of the four surfaces of the square billet l. The monitors K and K are respectively located just behind the magnetizing system J and J and in front of the feed rollers 34 succeeding both systems J and J. This is because the lower surfaces of the square billet I are deprived of the magnetic particle patterns by the feed rollers 34 and because the magnetic particle patterns on the surfaces of the billet I are collapsed by the vibration due to billet transfer, and the like.

Preferably the marking device L comprises, for example, paint powder sprayers interlocked with solenoid valves.

The operation of the apparatus shown in FIG. 5 is an follows: The magnetic particle patterns formed on the X-X and YY surfaces of the square billet I by the magnetizing system J and J are picked up by the respective television cameras of the monitors K and K to be converted into electric signals, and memorized in the memory-delay units M and M comprising tape recorders or the like, and then transmitted to the marking device L corresponding to the time lag and regenerated so as to effect simultaneous marking of the flaws in all the surfaces of the billet l.

While the invention has been described with particular reference to long square billets by way of illustration, it will be understood that the invention is not to be limited to the inspection of such billets but is applicable to rectangular flat steels and other materials.

The following example illustrates the application of the apparatus shown in FIG. 1:

Square billet l 100 mm square and 12 meters long Magnetizing system D: 200 volts a.c., 150 amp.

Flaw removing grinder 16: 60 HP. 500 rpm 610 mm dia., mm wide Black light projectors F: 2 units, watts each Flaw detecting and removing speed: 60 meters per minute One operator required It should be noted that the conventional direct current supply method (a) applied to the above described square billet (100 mm sq.) has allowed magnetic flaw detection at the rate of one piece per minute, requiring about six operators for the marking operation.

What is claimed is:

1. An apparatus for detecting flaws in elongated steel rigid workpieces, comprising in combination:

a. an elongated frame with at least one central grinding section therein;

b. at least first and second straight roller tables means extending outwards from said central grinding section for reciprocally moving workpiece past said central grinding section first in one and then the other direction at a predetermined level;

c. at least first and second magnetic particle sprayers respectively over said roller tables on each side of said central grinding section for respectively spraying colored magnetic particles over surface portions of a workpiece during its movement in the one and then in the other direction.

d. at least first and second A.C. energized electromagnets on each side of said central grinding section between said sprayers and said central grinding section, positioned below said predetermined level, and oriented such that when brought to said predetermined level their poles are disposed adjacent the two longitudinal sides of a workpiece as it passes towards said central grinding section, said magnets applying an alternating magnetic field to said workpiece, so as to cause said magnetic particles to cover flaws on said workpiece surface;

e. flaw removal grinding means at said central grinding section for grinding the surface portion of said 10 said first and second electromagnets away from the workpiece when not used on the workpiece to avoid a workpiece striking one of the electromagnets.

2. An apparatus as claimed in claim 1, wherein said tables have V-shaped roller means to move a rectangular workpiece, said electromagnets acting on adjacent sides of said workpiece. 

